Natural gas produced from wells contains water vapor and may contain other compounds such as hydrogen sulphide and sulphur dioxide which are generally preferred to be removed prior to the entry of the gas into a transmission line. Removal of such dilutants and contaminants is desirable to prevent dehydrate blockage, condensed water accumulation and assure proper operation of gas transmission lines by preventing corrosion thereof and to provide the gas which meets the heating value and other specifications usually set by the operator of the transmission line. A general method of removing the water vapor or other material has been to provide intimate contact of the gas with a liquid which will absorb the water or other undesirable material from the stream. Glycol dehydrators are designed to provide intimate contact of the gas stream and triethylene glycol which absorb the water vapor therefrom. Amine desulfurizers have long been used to provide intimate contact between the gas and a monoethanolamine to remove the sulfur compounds from the stream. To preserve the pressure of the natural gas stream produced such intimate liquid gas contact is normally provided in a vessel maintained at substantially the flowing pressure of the natural gas stream and the liquid is pumped into such vessel.
In glycol dehydrators attempts have been made to utilize the wet or rich glycol, i.e. containing water or water vapor, leaving the contacting vessel to provide at least a portion of the driving force to pump the lean or dry regenerated glycol into such vessel as shown in U.S. Pat. Nos. 2,990,910 and 4,026,681. The pump shown in the first mentioned patent has been in use for many years. Such pump is difficult to keep in operation, since it is very complex structure of pistons, check valves, interior slide valves and complex internal porting.
The use of a gear motor driving a gear pump through a direct drive coupling has been suggested (U.S. Pat. No. 3,067,590) for use in a refrigeration system to utilize the liquid flowing in the high pressure side of the system to drive the pumping of low pressure liquid. This is accomplished by interposing a gear motor in the high pressure line leading from the compressor to the accumulator and the gear pump interposed in the low pressure line leading from the accumulator to the evaporators. If such system operates as described, both devices are exposed only to liquid and no gas passes through either device. It appears clear if there is an operable system that the compressor supplies all of the motive power for the movement of the liquids through the system piping. Further, this patent suggests that the pump have a substantially greater cubic displacement than the motor. This clearly negates the passage of gases or vapors through the motor.
Other devices have been suggested to take advantage of fluid energy to move fluids such as U.S. Pat. No. 3,886,763 which provides a single sliding vane compressor-expander for a refrigeration system. A similar unit is shown in the U.S. Pat. No. 3,045,899 which discloses a single sliding vane motor-compressor for use in an absorption system for drying gas. This system suggests that the driving force of a first pressure stream be used to compress a second fluid pressure stream in driving it through a separate circuit.